1. Field of the Invention
The present invention relates to a method of setting the base energy level for an Auger Electron Spectroscopy (AES) analysis of a Titanium Nitride (TiN) film, and a method of analyzing a TiN film, or a semiconductor device having a TiN film thereon. More particularly, the present invention employs AES to conduct a quantitative and qualitative analysis for the nitrogen (N) contained in the TiN films of the semiconductor devices.
2. Description of the Related Art
Metal film or metallic nitride films are often used in the semiconductor device fabrication process. In order to establish proper processing parameters, it is necessary to carry out a precise quantitative and qualitative analysis of the nitrogen and metal in the metallic nitride films.
However, the nitrogen analysis can not easily be performed prior to or after the process. Moreover, the analysis of the nitrogen content in the TiN film is further complicated by the fact that the titanium (Ti) peak and the main nitrogen (N) peak overlap, making a precise qualitative and quantitative analysis more difficult.
Generally, a conventional Scanning Electron Microscope (SEM) may be used to analyze the wafer prior to the fabrication of the semiconductor devices. Also, a Transmission Electron Microscope (TEM) may be used to analyze the structure of metallic samples, for example, the crystal structure of the samples, by scanning an accelerated electron beam toward the sample and analyzing the diffraction pattern. Moreover, an Auger analysis may be performed in which the secondary electrons emitted from the surface of the sample surface are examined. Such methods are well-known to those of ordinary skill in the art and are commercially available.
The Auger analysis, or Auger Electron Spectroscopy (AES), uses a method where excited atoms having high energy levels are brought to low energy levels by releasing electrons. While analyzing a certain portion of a wafer, if electrons having a certain energy are scanned on the sample, excited atoms release secondary electrons called Auger electrons as well as X-rays. By detecting the velocity or the distribution of the Auger electrons, the surface state of the sample can be examined, and the presence of a certain atom and its relative amount can be detected by measuring the energy of the Auger electrons.
However, as described above for TiN films, the analysis of the nitrogen in the TiN film is complicated since the titanium (Ti) Auger peak and the main nitrogen (N) Auger peak overlap, making a precise qualitative and quantitative analysis difficult. See, S. Hofmann, "Characterization of nitride coatings by Auger electron spectroscopy and x-ray photoelectron spectroscopy", J. Vac. Sci. Technol. A 4(6), November/December 1986, pp. 2789-96; and M. Willemsen et al., "In situ investigation of TiN formation on top of TiSi.sub.2 ", J. Vac. Sci. Technol. B 6(1), January/February 1988, pp. 53-61. As described in the references, the Ti Auger peak of a standard Ti material (FIG. 1) and the Ti+N Auger peak of a standard TiN (Ti+N) material (FIG. 2) overlap, making it difficult to analyze the nitrogen content of the TiN film.
FIG. 3 and FIG. 4 depict the spectra of a semiconductor device having TiN/Ti films as a barrier metal film, wherein the intensity and atom concentration are correlated to the sputter time, respectively. Note that the peaks of the N and the Ti overlap so as to make the separation of the N peak difficult, which decreases the reliability in calculating the component ratio. The un-designated arrows in FIGS. 3 and 4 point to a region wherein, although the intensity value of the titanium and nitrogen components appears to overlap, the nitrogen component is not present as shown by the elapsed sputter time for a sample comprising TiN/Ti/SiO.sub.2 /Si-substrate.
Accordingly, there is a need for an AES analysis technique for accurately determining the quantitative and quantitative analysis of the nitrogen content within a TiN film so as to improve the reliability and production capacity of the semiconductor devices having such TiN films.